Two types of typical circulation pattern for persistent extreme precipitation in Central–Eastern China

Abstract

AbstractTwo characteristic circulation patterns responsible for persistent extreme precipitation (PEP) events in Central–Eastern China are identified using a composite analysis: a double‐blocking high type and a single‐blocking high type. The double‐blocking high type is characterized by the development of two blocking highs near the Ural Mountains and the Sea of Okhotsk, with a trough between them. This long‐lived pattern continuously steers cold/dry air from mid–high latitudes to Central–Eastern China, where it encounters anomalously warm/moist air from lower latitudes conveyed by intensified southeasterlies associated with a westward shift of the western Pacific subtropical high (WPSH). The single‐blocking high type is characterized by the appearance of a blocking high to the south of Lake Baikal. This blocking high is accompanied by a deep trough located to its east, which extends into the southern Yangtze River Valley. The anomalous anticyclone associated with the westward extension of the WPSH is located further south and slightly east of that observed during the double‐blocking high type. Accordingly, the intensified southeasterlies convey anomalously moist air to the southern and eastern parts of Central–Eastern China. In the upper troposphere, the displacement of the South Asian High and jets favours divergence for both typical circulation patterns.The comparison between the composites and additional cases that share similar circulation patterns but do not result in PEP in Central–Eastern China suggests that PEP events typically result from concurrent combinations of persistent anomalies from lower to upper levels, rather than from isolated anomalies of specific weather systems.